The present invention relates to a method and apparatus for filling cartons or similar containers with sucessive stacks of articles. It is particularly, but not exclusively concerned with filling stacks of tea bags or similar infusion packages into cartons.
In a typical infusion packaging machine, measured doses of tea or another infusion are deposited in two parallel rows on a first moving web of thermoplastics coated filter paper whereafter a further web is laid over the first and individual pockets of infusion formed by heat sealing the webs together. The web is then cut to form adjacent separate packages or adjacent packages joined along a perforation line. These packages then move to a collation chamber where they are stacked and from where the adjacent collated stacks are moved into a device which inserts them into the carton. This latter device usually comprises opposed vertical plates which hold the stacks between them and which are moved down together into the carton where they are moved apart to deposit the stacks, whereafter they are retracted to receive the next pair of collated stacks. The carton is then moved forwardly by a suitable conveying means in a stepwise manner, by such an amount so that when the insertion device next moves downwardly, the carton will have moved forward sufficiently for the device to deposit the next stacks just behind the first previous ones. This sequence is repeated until the carton is full, whereupon a subsequent carton is moved beneath the plates for filling, and so on. The filling process is thus fully automated.
The respective sizes and shapes of the infusion packages and the cartons have traditionally been such that the sides of the stacks are supported to some extent by their frictional engagement with the side walls of the carton during its stepwise forward movement which is normally sufficient to prevent the stacks falling backwardly due to inertia. However, this may not be the case if for example a carton is oversize or if the infusion package is of a non rectangular shape, for example circular, which would lead to relatively poor support of the stacks by the side walls. Furthermore non-rectangular packages, for example circular packages, may be inherently less stable when stacked than rectangular packages. If a stack falls backwards into the carton, this will prevent subsequent stacks being placed satisfactorily.